Stomata that open and close in response to changes in light intensity.

Many air spaces in the lower mesophyll layer to allow diffusion of carbon dioxide and oxygen.

A network of xylem that brings water to the leaf cells and phloem that carries away the sugars produced in photosynthesis.

Outline of Photosynthesis:

6CO2 + 6 H2O ----- light -----> glcose + 6H2O

Photosynthesis is a complex metabolic pathway involving many intermediate reactions.

There are three main stages of photosynthesis:

Capturing of light energyby the chlorophyll.

The light dependent reaction -this is when light energy is converted into chemical energy. An electron flow is created by the effect of light on the chlorophyll and this causes photolysis - the splitting of water molecules, into protons, electrons and oxygen. Producing the products reduced NADP, ATP and oxygen.

The light independent reaction -this is when hydrogen ions are used to reduce carbon dioxide into sugars and other useful organic molecules.

Structure and Role of Chloroplasts in Photosynthesis:

Photosynthesis occurs in the chloroplasts of the leaf, they vary in shape and size but at typically disc-shaped and are also surrounded by a double membrane.

There are two distinct regions of the chloroplasts:

The grana are stacks of up to 100 disc-like structures called thylakoids where the light-dependent reaction occurs. Within the thylakoids is the photosynthetic pigments called chlorophyll. Some thylakoids have tubular extentions that join with thylakoids in adjacent grana, called inter-granual llamellae.

The stroma is a fluid-like matrix where the light independet reaction occurs. There are a number of structures such as starch grains, within the stroma.

The Light Dependent Reaction:

This involves the capture of light whose energy is used for two purposes:

To add inorganic phosphate molecule to ADP to make ATP.

To split water into hydrogen ions and electrons. As the splitting is caused by light, it is known as photolysis.

Oxidation = when a substance combines with oxygen and loses electrons, resulting in energy being given out and so energy is lost.

Reduction = when a substance loses oxygen and gains electrons, resulting in energy being taking in and so energy is gained.